Dispersants compatibility with polymer

Aid in the uniform dispersion of additives. Make powdered solids (e.g. particulate fillers with high energy and hydrophilic surface) more compatible with polymers by coating their surfaces with an adsorbed layer of surfactant in the form of a dispersant. Surface coating reduces the surface energy of fillers, reduces polymer/filler interaction and assists dispersion. Filler coatings increase compound cost. Fatty acids, metal soaps, waxes and fatty alcohols are used as dispersants commonly in concentrations from 2 to 5 wt %. 

Microlith [Novartis]. TM for organic pigment stir-in dispersions compatible with a broad range of organic solvents and polymers. 

The discovery of carbon nanostructured materials has inspired a range of potential applications. More specifically, the use of carbon nanotubes in polymer composites has attracted wide attention. Carbon nanotubes have a unique atomic structure, a very high aspect ratio, and extraordinary mechanical properties (strength and flexibility), making them ideal reinforcing compounds. Moreover, carbon nanotubes are susceptible to chemical functionalization, which broaden their applicability. For instance, surface functionalization of carbon nanotubes is an attractive route for increasing their compatibility with polymers in composites, also improving the dispersability in raw materials and the wettability. 

Many of the sohds used in a dispersed state in pol)nners have high energy, hydrophilic surfaces. Examples include titanium dioxide, coloured pigments, mica and even metal particles. Such powdered sohds can be made more compatible with polymers by coating their sm-faces with an adsorbed layer of surfactant in the form of a dispersant. Sodium di-alkyl sulphosuccinates, more commonly used as wetting agents, have been employed for this purpose. 

Since most inorganic particles are not very compatible with polymers, mechanical agitation and ultrasonication are usually applied to facilitate particle dispersion. Particle surface modification and surfactants are also used to increase the compatibility between nanoparticles and the polymer matrix. Based on the original medium where the nanoparticles are dispersed, the manufacturing process for making polymer nanocomposites includes melt... 

Comparison of Table 5.4 and 5.7 allows the prediction that aromatic oils will be plasticisers for natural rubber, that dibutyl phthalate will plasticise poly(methyl methacrylate), that tritolyl phosphate will plasticise nitrile rubbers, that dibenzyl ether will plasticise poly(vinylidene chloride) and that dimethyl phthalate will plasticise cellulose diacetate. These predictions are found to be correct. What is not predictable is that camphor should be an effective plasticiser for cellulose nitrate. It would seem that this crystalline material, which has to be dispersed into the polymer with the aid of liquids such as ethyl alcohol, is only compatible with the polymer because of some specific interaction between the carbonyl group present in the camphor with some group in the cellulose nitrate. 

In addition to acting as impact modifiers a number of polymeric additives may be considered as processing aids. These have similar chemical constitutions to the impact modifiers and include ABS, MBS, chlorinated polyethylene, acrylate-methacrylate copolymers and EVA-PVC grafts. Such materials are more compatible with the PVC and are primarily included to ensure more uniform flow and hence improve surface finish. They may also increase gelation rates. In the case of the compatible MBS polymers they have the special function already mentioned of balancing the refractive indices of the continuous and disperse phases of impact-modified compound. 

Hydrophilic/hydrophobic properties. In water-based systems, the filler should be compatible with water because filler dispersion occurs in an aqueous medium before a polymer emulsion is added. In general, most fillers are hydropho-... 

A better combination of fiber and polymer is achieved by an impregnation of [44] the reinforcing fabrics with polymer matrixes compatible with the polymer. Polymer solutions [40,45] or dispersions [46] of ]ow viscosity are used for this purpose. For a number of interesting polymers, the lack of solvents limits the use of the method of impregnation [44]. When cellulose fibers are impregnated with a bytyl benzyl phthalate plasticized polyvinylchloride (PVC) dispersion, excellent partitions can be achieved in polystyrene (PS). This significantly lowers the viscosity of the compound and the plasticator and results in cosolvent action for both PS and PVC [46]. 

Oils of the three types are offered in a range of viscosities and this will influence their processing character to some extent, although there is little evidence that it will have much influence on the ultimate compound physical properties, at least in natural rubber compounds. The small additions of oil to a compound help with filler dispersion by lubricating the polymer molecular chains and thus increasing their mobility. There will also be some wetting out of the filler particles which enables them to achieve earlier compatibility with the rubber and improve their distribution and dispersion speed. 

While conductivities of nanocarbons dispersed in polymers fall short of those of metals, a variety of applications can be unlocked by turning an insulating matrix into a conductor, which requires only small volume fractions that can therefore keep the system viscosity at a level compatible with composite processing techniques. Of particular interest are novel functionalities of these conductive matrices that exploit the presence of a conductive network in them, such as structural health monitoring (SHM) based on changes in electrical resistance of the nanocarbon network as it is mechanically deformed [30]. 

With copolymers it is of importance whether a one-phase or a two-phase structure is formed (random- or block-copolymers). In a similar way we see with polymer blends two (extreme) cases real blends of wholly compatible components, and dispersions of incompatible ones. In the first case, which seldom occurs (e.g. PS with PPE) we find a single Tg in the second case two T s, namely those of the two components. 

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